This invention relates to an axle assembly for a vehicle and a vehicle comprising an axle assembly via particularly but not exclusively a material handling vehicle.
In conventional vehicles, steering is achieved by pivoting one set of wheels, usually the forward set of wheels. In particular applications, however, such as for material handling vehicles, it is desirable to provide a vehicle with different steering characteristics, for example to allow a tighter turning circle. Skid steer vehicles operate by driving wheels on opposite sides of the vehicle at different speeds or in different directions, to provide a very tight turning circle or even spin on the spot. Where the wheels are provided with tyres, however, this result and “scrubbing” between the tyres and the surface on which the vehicle is travelling and leads to tyre wear, and skid steering is generally regarded as most appropriate for the vehicles with short wheel bases. Where a vehicle has a longer wheel base, it is known to provide steering on both axles, such that the front and rear wheels can be controlled either such that the front and rear wheels are pointing in opposite directions to provide a tighter turning circle, or may be rotated in the same direction to provide so called “crab” steering which allows the vehicle to move diagonally.
To provide longer-wheel based vehicles with spin turn capability, it is known from vehicles such as the Jeep Hurricane to provide a so called “spin turn” capability wherein each wheel is pivoted about a generally vertical axis such that each wheel extends tangentially or as close as tangentially as possible to a common circle. By driving one or more of the wheels, the vehicle can then spin in position. Such a mechanical configuration is complicated to provide as the wheels of the end of each axle must revolve in opposite directions and drive must be transmitted to the wheels. The known arrangement is heavy, and mechanically complicated.